Power-line communications (PLC) involves transmitting data using power-line cables (power cables) as the data transmission medium. Power-line communications modems act as network bridges that convert data, for example, between an Ethernet network and the power-line.
In an underground coal mine, PLC may be used to transfer data between an enclosure on a mobile machine (e.g. longwall shearer, continuous miner) to an enclosure of a power centre (also known as a distribution and control box, DCB). Thus one power-line modem may be installed in each of these enclosures and the network data travels between them on a power cable connecting the power centre and mobile machine. In some alternatives, the PLC may be used to transfer data between an enclosure of stationary equipment (e.g. ventilation fans, pumps) and the power centre.
Power-line communications are an attractive option for data transmission in underground coal mines for the following reasons:                they use the existing, rugged power-line for data transmission;        no need to lay extra data transmission cables; and        modem equipment may be housed in existing protective enclosures so that they are not exposed to mining environment.        
However, the characteristics of power-line cables used in mining mean that effective data transmission is limited to power-line cable lengths. In some practical examples, effective data transmission may be at a maximum of approximately 500 m of a power cable between power-line modems.